Tire pressure indicating and recording device



Feb. 23, 1954 D. M. LEN-rz 2,669,876

TIRE PRESSURE INDICATING AND RECORDING DEVICE Filed July l5, 1950 V4 Sheets-Sheet 1 U56 5 ya ATTORNEYS Feb. 23, 1954 D M, LEN-rz 2,669,876

TIRE PRESSURE INDICATING AND RECORDING DEVICE Filed July l5, 41950 4 Sheets-shewi 2 72 'HZ 770 32 72 72 y" f al 72 j 5 72 72 72 72 f6 f6 f6 f3 5 ya c' d Q J0 2 20 *1' 20 Z0 AH; PRESSURE Pff' 7 INVENTOR. MV/0 M. 6A/TZ ATTORNEYS Feb. 23, 1954 D. M. LENTZ TIRE PRESSURE INDICATING AND RECORDING DEVICE Filed July l5, 1950 4 Sheets-Sheet 3 A l l 145 M5' if@ INVENTOR.

0 4 wo M En/rz rT/QNEYS BVM if @WMZ/ Feb. 23, 1954 D, M, LENTZ 2,669,876

TIRE PRESSURE INDICATING AND RECORDING DEVICE Filed July l5, 1950 4 Sheets-Sheet 4 AIR PRESSURE MULTIPLY BY lo JNVENTOR. 24v/o M ewrz rme/veys Patented Feb. 23, 1954 TIRE PRESSURE INDICATING AND RECORDING DEVICE David M. Lentz,-Maple Heights, Ohio, assignor to Edward K. Brown, Shaker Heights, Ohio, as

trustee Application July 15, 1950, Serial No. 174,046

(Cl. 'I3-390) 9 Claims.

The present invention relates to apparatus for indicating and/or recording fluid pressures, particularly in environments in which it is desirable to have a warning of pressure variations from a predetermined range, such as in the air pressure of vehicle tires. The present application is a contnuation-in-part of my now abandoned U. S. application Serial No. 778,869, filed October 9, 1947, for Tire Pressure Alarm and indicating Device.

An object oi the present invention is the provision of a fluid pressure indicating apparatus having a warning signal operative when the fluid pressure deviates from a predetermined range and an indicating mechanism adapted to indicate the exact fluid pressure outside of the predetermined range.

A further object of the invention is the provision of a fluid pressure indicating system having a warning signal which is operative when the pressures in one or more of a plurality of luid pressure containers, such as the tires of a vehicle, deviate from normal.

A further object of the present invention is the provision of a fluid pressure indicating system for indicating pressures in a plurality of uid containers, which system includes a fluid pressure indicating device and a Warning signal, which signal is operative to indicate abnormal fluid pressures in any oi the containers, and the indicating device being adapted to selectively indicate the pressure in the individual containers.

Another object of the invention is the provision of a new and improved uid pressure indicating system comprising a device for printing a record of the fluid pressures in one or more containers, a dial indicator for selectively indicating the pressures in one or more of the containers, and a Warning signal operative when the liuid pressure in any of one or more containers deviates from a predetermined range.

Other objects and advantages of the invention will be apparent from of preferred forms of being had to in:

Fig. l is an elevational view of a vehicle wheel with one form of an air pressure responsive electrical resistance device attached thereto;

Fig. 2 is a sectional view taken substantially along line 2 2 of Fig. 1;

lFig. 3 is a sectional View of the electrical resistance device;

Fig. 4 is a sectional on line 4-4 of Fig. 2;

the following' description the invention, reference the accompanying drawings, Whereview ltaken substantially Fig. 5 is a wiring diagram of the mechanism for indicating the air pressure in a plurality of tires of an automotive vehicle, which mechanism includes a signal for indicating abnormal air pressures in the tires;

Fig. 6 is a fragmentary sectional View of a vehicle Wheel and axle showing the pressure responsive electrical resistance device attached to the vehicle in an alternative manner;

Fig. 7 is an elevational View of a dial indicator for indicating air pressure in the individual tires;

Fig. 8 is an elevational view of a vehicle wheel having another form of pressure responsive elec trical resistance device mounted thereon;

Fig. 9 is a sectional view taken substantially along line 9`9 of Fig. 8;

Fig. 10 is a fragmentary end elevational view of the resistance device shown in Fig. 8;

Fig. 11 is a fragmentary view taken on line ll-Il ofFig. 9;

Fig. 12 is a wiring diagram of mechanism for producing a warning signal in the event of an abnormal air pressure in any one of a plurality of vehicle tires and having indicating means to provide a printed record of air pressures existing in the individual tires from time to time and a dial indicator to register the exact abnormal pressure in any selected tire; and

Fig. 13 is a fragmentary elevational View of a recorder which is shown diagrammatically in Fig. 12

The invention contemplates the provision of a pressure responsive variable resistance device adapted to respond to fluid pressures such as the air pressures in individual tires of a vehicle. The resistance device includes a contact movable over a suitable resistance coil by a pressure responsive device actuated by the fluid pressure, and a portion of the resistance coil in the path of the contact is insulated from the movable contact, or otherwise blocked therefrom, whereby the Contact makes electrical connection with the coil only When the iiuid pressure is above or below a predetermined or normal range. The resistance coil is connected in an electric circuit which includes an electric signal device and is capable of energizing the signal so that in the event there is abnormal fluid pressure the signal is energized. A current responsive indicator, preferably of the Wheatstone bridge type, is adapted to be selectively connected in the resistance circuit and which registers such current in appropriate terms, such as pounds per square inch of fluid pressure in the pressure responsive devices. The indicating system is particularly suitable for indicating the pressures in a plurality of fluid containers and in that event a pressure responsive resistance device is connected with the individual containers and the signal is in parallel circuit with the resistances so that variation of fluid pressure from a predetermined range in any of the containers results ingopdrationofthe signa-l.' The indicator is adapted. to be selectively connected'iw-ithanyone of the pressure responsive resistances to indicate the individual pressures.

In one form of the invention, avrecording Adevice responsive to the current inA the resistancecircuit or circuits is provided which prints a record of the fluid pressures'atgfreuuentiinte vals and, preferably, a signal deviceislproyfidedil in conjunction with the recorder to indicate abnormal fluid pressures according.: to. currelflt.val-` ues in the resistance circuit or circuits. Also, the recorder may be temporarily disconnected from the resistance circuit or circuits and a dial ttglgcrfndieatorf selectivelyy connected with the indiyidual-L circuit, or(4 circuits to secure a reading.V Gambe; exact abnormal. fluid pressures.v

Baeerang. now toI thedrawings, orieform; of the invention is shown in Figs. 1 throughl andl itA comprised-,az mechanism for indicating; the air pressure four pneumatic tires ofa vehicle,Y aithoughgitfisto; b .e understood that the mecha.- nism -could be: used in connection withV other ml G llid containers1 orv with-y more orfewer tires; 0.1"; containers.. ify desired- Reierringto-Figlga vehicle wheel W having @..nneuruaticftirer is mounted on the axle- X' of the vehicle;-imthefusualmannen A. suitable measures responsive rcsistancey device indicated generally at 20 is attached; tog-the wheel'andgin, tbez-ffoim-.shcwni it.comnrisesraumetallic cylinder 2l having Qneeendisealed by a can. 222 andthe-1v apposite and closed; by"I an: end .member 23. The cap and end member may be attahedito.; the cylinderrin any suitable-r mannery but, are here shown threadedongthecylinder; The endf mem.y loer- 213;- has; aynippleformation.l 24 and air` paee V2.5; therein; leadingl from'. the nipple. 241 to the.1 @entrai portion. of; innen face of: the mem-Y borrto prov-ide. Communication. between therme, immr Q'f the: Cylinde? 24. andi the. interior' ofi the tire by way of a tube lrattachedzatzone.:end= to theenippleiiandattheiother end; to. a branch ojgtheftire. iii-dating;- stem; 2.7:.. The 1 underside off the end member 28 is bored and tapped to re.-A QSil/-c ai.. bolt', 28./- by Whi'ch. the devicefis'seeured taabracleet; 23- attachedi to the. wheel' bic a. studi 1103.15 airldnntzi;

theyfQ-rmshown inf Fig. l. the. device-26 isJ mountedc. to; one; side'. of; the; axisA of rotationA of? thef-wheel-Witht the axis, of rthe cylinder 2 l: extend.v in@ inea; planegnormal. tof the axle Alterna. tivelm-thegidevicej could be mounted with: the axis: ofrcyflimier;v Zeil extending.y parallel to the axle as. drowiriuiEig: 6. In either'case rotation offthe deyicesrby thev wheel do es-not cause erratic action ofzthefvariouspartsby centrifugal force;

Amis-ton: 3.2 reciprocates ini thev cylinderA 2t' and has.annetallic--rodi-l attachedlthereto. which pro jectsaupwardly through anV opening through.` capl 2-22, Thev piston. 3'2 has: a sealing ring-34f carried ina peripheral grooveftherein, Awhich ring is-preefr-.alolyf` formed of` resilient materiali. suchv as ay suitable?g soscalledsynthetic rubber, and" forms-arr airtighta seal betweenthe; piston and; cylinder-1v A; compression: spring; 3.6 surroundsthe. piston rodi 33a and; is interposed. between the` piston andE 2.2; to.- opposemovement.. ofiv the pistonv in-y the;- unward'; directouasgviewed'in, Fig: TheL iii);v

tension of the spring is such that the posit-ion of the piston in the cylinder corresponds uniformly to the air pressure in the cylinder beneath the piston, at least over the major range of movement of the piston.

A variable electrical resistance 38 is attached to theI exterior-ofi the cylindengZl, which resistance-preferably comprises a core 39; formed of a suitable dielectric material having an axial opening 4 extending therethrough, and wire 42 coiled aboutthe come... The wire 42 is preferably embeddedgininsulation 43, except for a longitudinal strip of the outer surfaces of the wire coil which is; bared by,4 ai gap 44 in the insulation. The-gap 4:4 bridged by a relatively short segment of insulation 45, the purpose of which is explained hereinafter. A terminal bolt 46 and nut 4'! are provided for connecting one end of the# coiled wire 42 with a circuit to be described hereinafter.

Thepiston rod 3,3 has a metallic. contactcarrying rod; iS-attached theretowhich is adapted-to extend into` theV` axial opening of the core: 39 and to: be.v guided therein as the piston 3.2, reciprocates in the cylinder. The rod 48- has ai contact do attached. thereto; which is adapted" to; ride in the gap 4.4. and to contact the exposed` surfaces of the coiled wireA 4.2 as the: piston 3.2-A movesin thecylinder.` It, will be seen that. by:

connecting one end of the wire 42 and the mov.-A

able contact, 5.91 in i series; in' an. electrical circuit a variable resistance may beLprovided which corresponds to the air pressure' in' the.: tire: to which: thev cylinder 2i is connected.

The springt-iszadaptedto resist upward move-V ment of piston 32; tothe extentthat when theair pressure within the cylinder 2|y below the: piston: is withinadesired normal range, for example 35- to 37` lbs., the; contact .56 engages the insulating material which bridges the gap 44- in the. insulation; 43 andfthereby interrupts the. circuit through; the. resistance device. 1f theV pressure is above or below the-normalfrange, thecontact:` 581 engages.` theV exposed portions of the coiledi wire 421 andprovidesa resistance correspendingv to-theiair/pressure; Itv will be appreciated that thenormal range of operation: of? the` resistance ydevice may be determined bythepositionl ofthe insulating material 45-'onthe coil 42:r and. the limitsof' the rangedetermined byy the: width ofi the materiali One end of the coiled-wire 42 lis. connectedfwithf. a source; of,` current-1 byawire-l 55wl1ichV isA attachedi at.- one end. to=the\coi1 at the termina-ll 41; and-thefopposite-end-of which is-electricallyconnected' toa collectorring- 561 attached to the wheel W; preferably inside thebrake drum D; The-collector ring 56-isv attached to the outer walloffthe` drum D` by boltsI 5l; which extend through' the wheel plate and which are-secured" by nuts 58 threaded thereon; The ring 56l isinsulated from the-wheel byinsulating grommets and washers 66? interposed between-the'ring and'`4 theibralee drum and bolts 57,' asfshown. Current is suppliedv toY the collectors ring 56 by a1 brush 6| supported for longitudinal movementjrr a threaded tube- 63"- havingA anV4 insulatingsleeve 64l therein and` which tube is' attached in; an opening through the innenwall 65- of the brake drum D` byv a pair-of" nuts 66;y threaded on the tube and one on each side of the wa1l. A plugV 68t is-threadedf into one end ofthe insulating sleeve 64, which plug has a terminal nut169"v threaded on7 the-outer-end thereof? and-'the inner end engages a compression springt-IJI which-urges the brush 6I outwardly and into engagement with the ring 56. A wire 12 is connected to the plug 68 by the terminal nut 69, which wire leads to a source of current, as described hereinafter.

The opposite end of the resistance coil 42 is grounded through the Contact 50, metallic rods 46, 33, spring 36, cylinder 2I, bracket 29, wheel W to the frame of the vehicle through the axle.

It is to be understood that each wheel of which the air pressure in the tire thereof is to be indicated, is equipped with a pressure responsive variable resistance device 28. In the embodiment shown, four devices 29 are used and are illustrated diagrammatically in Fig. 5 as mounted on wheels a, b, c, d, respectively, like reference char; acters indicating like parts.

The wires 12 may be connected with any suitable source of current, and are shown connected with the positive electrode of a conventional storage battery B, which supplies current for opera.- tion of the vehicle, through a circuit including a rive pole, manually operable double throw switch 13, wire 14, solenoid 15, and wires 16, 11. Preferably, a switch 18 is connected in series with wires 16, 11 and is adapted to be opened and closed by the vehicle motor ignition switch mechanism as the ignition switch is opened and closed so that the mechanism is deenergized when the vehicle engine ignition is turned olf.

The switch 13 86, 81, 88, 89, which are movable by a common operating member to engage, respectively, contacts 9|, 92, 93, 94 which are all connected with wire 14. By this arrangement, all of the variable resistance devices 20 are electrically connected and disconnected with wire 14 simultaneously. Contact 90 is adapted to engage contact Q6 when contacts 86, 81, 88, 89 are open and to be moved from contact 96 as the other contacts are closed, the purpose of which appears hereinafter. The switch 13 is preferably located conveniently to the operator of the vehicle, such as on the instrument panel of the vehicle.

The solenoid 15 is adapted to close a normally open contact 80 when energized by current voltages such as those of the currents through the resistance devices 20, which contact is adapted to close a circuit through a signal device, and in the form shown it is an electric lamp 8l, the

circuit for which lamp includes battery B, wire 11, switch 18, wires 16, 82, contact 8U, wires 83, 84 to ground. The signal lamp is mounted in any suitable location in the view of the vehicle operator. As may be seen, when switch 13 is closed, the signal lamp is lighted in the event a circuit is completed through any one of the resistance coils 42 of the devices 20. As explained hereinbefore, no circuit is completed through the resistance coils `unless the air pressure in the tire with which the respective devices are connected is above or below normal.

A dial indicator A isV provided which is adapted to be responsive to the current potentials in the respective resistance coils 42 and to correspondingly move a hand 91 relative to suitable indicia to provide a reading in air pounds, as illustrated in Fig. 7. Preferably, the indicator is an ammeter connected in the bridge of a conventional Wheatstone bridge circuit, three arms of which are respectively -formed by resistances H18, HH, |02 and the fourth arm of which can comprise any selected resistance coil 42 of the respective devices 20. As shown, ammeter A is connected between the resistances IUI), VIIlI and preferably comprises contacts IIJZ and the respective resistances of the devices 20. A suitable resistance I03 is provided in series with the ammeter. The indicator A is located in view of the vehicle operator, as on the instrument panel.

The resistance coils 42 of any of the devices 20 can be selectively connected in the Wheatstone circuit by a selector switch, I I8 which includes a sweeping contact I II adapted to be rotated manually to successively engage xed contacts II2, I I3, I I4, I I 5 supported in a suitable switch housing indicated at IIB. Contact III is connected with the Wheatstone bridge circuit through wire H8, contacts 90, 86 and wire II9. The contacts H2, II3, H4, H5 are connected with the wires 12 of the respective resistance devices 20, and by properly positioning the contact II I the ammeter A can be made to indicate the potential in any of the resistance devices desired. The switch I I0 is located convenient to the vehicle operator and select which device 20 is to be connected in the Wheatston-e circuit.

Preferably, the ammeter A is set to throw the indicator needle 91 thereof `to one extremity of the dial when no current is passing through the resistance coils of the devices 20, which occurs when the tire pressures are normal, and the dial has a mark to indicate this position, as 'may be seen in Fig. 7. In the form shown, when the Wheatstone bridge circuit is deenergized, as by opening switch 18, the needle 91 will rest at the position marked Ofi Normally, when the vehicle is in operation, switch 'It is closed and the switch 13 is moved to the posi-tion in which itconnects the wires 12, with wire 14 thereby setting up a circuit from the positive terminal of thebattery through solenoid 'I-5, wires 12, brush 6I, collector rings 56, resistance coils 42, -contact arms 50, to ground. When the air pressure in all of the tires is normal, contacts ride on the insulating bridges 45 rather than engaging the coils 42 and no circuit is. established through any of the resistance devices. In the event the air pressure in one or more of the tires becomes abnormal, either above or below the normal pressure, the contact 5U of he device 20 involved is moved into engagement with the resistance signal lamp 8l` which warns the operator of the The operator may then its circuit. The operator then moves contact I I l air pressure.

By this arrangement the vehicle operator is immediately advised by the signal light 8| of an abnormal air pressure in any one of the tires and he mayimmediately readily ascertain by the circuit through sole referencejtoithe amm'eterderthe:i selectcnswiteh ixliicl'iftire.y or( tiressares affete'andtto what exatent.'I Thee mechanism isi extremely: simple: and reliable andiv it; is. only: necessary`v to.y provide; but one ammeter in conjunction with thezfsignaidef vice; regardless@ of the nu ber: off tires to'.A be checked;

It'. isV quite^-\ common .inf thex trucking andi bus industries. for a separate; company; croperator tofcontractiwithi buszor truclif. operatoifsztolservice an@ rnaini'faiiry tlfiex tiresl of tlievehicles.. It has been., found`vby the tire servicing@ companies .i or operators,L that thee tire users.l aree frequei'itly.V lax inn carrying proper tire pressures and-'1y that the life of fthe l tires 1 isl materiallyd shortened for this reasoni One-bfl theI objects of." the-1 presentinventiorr is-vto provide-mechanismiirfilrnishing-a printed recordiof air: pressures in tlieseveralitires of vehicles whereby-'- the tireisupply-vcempanyr or operator may ascertain i Whether orfnote the tires have'been abused by over 'or under inflation, and to'. Whatiext'ent, and:` therebyftale -stepsto correct the diiculty. Also, this typeofi'mechanism will cause the vehicle operatort'oqoay-U close attention to the tires asfy his'-l negligence vcanlie-readily' de"- tectedby thoselinf authority. Accordingly; I-fhave provided a mechanismI which in additionv to havinga? signalv and'` dia-l indicator1V such -1 as that` described? liereinbefore, includes a" printing-mecha nisrrrV adapted; to Eprint on ak strip of tape a record. ofi any abnormal" airf pressures which may exist from' time to time irr'tliei'ndividualtirea The form of the invention just mentioned?, is shown in Figs. Sltofli whiclifmechanismincludes awpressureresponsivearesistance device*A 6 which sliownf attachedl toa wheeliW hav-ing` a pneumatic tirelT mountedltliere'on: The wheel W isrjournallediontheiaxlerX'ofavehicle in' a corrventional manner.l

'Phe-- device El includes a suitabl`e-cylinder |l I T. attached'tothelwheelby a;l strap bracket ||8 Which1is=secured-to-a Wheelt stud ||9i"by a nut' |250? The ends 'of f the" cylinder arefclcsed by4 an endfvfa-ll |22 anda closure'plug |23 The wall |l22flias-fa centralopening thereirr andarng |25 is` attached toA the inside ofi' the Wall` concentric with the'u opening therethrough; The sides` of thea opening andI the" interiorcof*v the ring` are threadedi toI receive-a tubular nippley |25 which isf-seeur-ed'lin place'byfanm |21 threaded' .on the exterior thereoff' and? engaging, the. outside off Wall-i |122? A suitablej expansible chamber; such as".a;ex: ible metallicbellows` |39, has' one` en'dr` attachedv tolthefri-ng |25 and is-hermetically sealed'to the;v ring;- andthe-#opposite` end1 isiclosediby a Wall I 3|; Then interioroff` the bellows" |30" is' subjected to` they air pressure'within the tire T" and'. is con,- nected with theA treinteriorbyv a tube; |33Aone end of whichu isconnected with theztire inating., stem |34 'andy tlieotherendA with the nipple; |26 sof that they bellows expands and4 contracts; a'cf -cordingto air pressurewvithin theitire' Tf;

plate IB'isattaclied' to tlie endwall |31"` of thebellows: and "hasia' stem |131' which projects'. loosely into` er bore |38* formed: in a. tubular'pro jection |40 on' the plug-, I23 A'. coil' spring; |41 surrounds'the projection`A |40' and' stem |31 ,L and' is` interposed between the plug; |23 andplatje, 3E."

to oppose expansion of the bellows |30; The. opposition of the spring. to expansionbfthe bel'- lbws'i's' such that.' themovemerrtilofthe, bellows.. is-proportional teA the `air pressure in the tire.

AJ stripjv typeel'ectri'cal; resistance. |44" atie.

rating materiab |48.. 'Itlieil wire maybe wrapped in;v coils"A alumina:` hat core or: itimay: be 'formed'. of

aserieszoi closreirerseebendslmthe present em;- bodiment, itisnsh'oyrn: in the llatter:ormuarrd'..the insulatiornelectricallwseparatesltheadacentsege ments ofthezwire:

"Eherinsulation MBE has twoi aligned; gaps'` |432 |'Mkvrliiclrextend;v longitudinally: oizthezresistance mit and areespacedzbv; aebridgezoi insulation; 'Ilfiewtrer exposed;A the ganse |485; |49 is.- bare emdziso adapted;L to. makerelectrical contact. with' a2 movable: contacter |5|2v which is attached to the;plate:A |136. andi moves inar the: gaps'` |248; |491 as the:v bellows |30/ expands` andy contracts.. The resistance |44 is positionedarelativato. ther-bale lows. so: that?when;normal tire-pressures exist, Contact; |5|a rests: on the insulation bridge andf. in: the:l arent: oi: above normalf or: belowl normal tirerV pressures; thecontact.; |^5|f engages the wire Misimthelgapsf 49( and. M8y,respectively` l'ire'A |z415i extends throught an: opening inL the side-.f oi?. the.' cylinder: |,=|.f't and: is coi'inectedlto1 a collectorfringt inside the-brake drumiofthe Wheel; similar: to; the. collector ring SiiA described: hereinbefora' Rreferably; thewire iltzis covered'btE suitable insulation Hirsi which extendsnsid'e the cylinder: |-I|'|.;.and a-.suitable sealingcement` l-iiltv is interposed between: theeopening'inl the cylin den and tberinsuiatiemtric providei ai hermetic seal. Breferably-tnea cylinder.' Hlii's sealed to preventi the: entrance: of: Waterir etcz, howeeV-er, it.- may; be: desirable; in' some: instances to proyide,` a breathing opening; the;v cylinder.' or

I to.-evacuate;-thercylirrderatcna;certainiextent'..y

Onefend o,;w-ire M5 islconnectedlwitha source of.. current througbztlxe collettori ring, asl is de scrib,ed-ilr1ereinaiterq and tnefoppositefend isfconnectedv to the ground; byt Way of the'frame of ther` vehicle.-`v which; ground.; connection: includes' Contact |-5:| A.. plate: |@36i2 bellows: |30; ring` |253;v cyl# inder LI 1;. bracket:v lil-Bite the Wheel-Wly andfrom1 the Wheel; to, the?` axle; ttmoueh a z strip|- contacter |58 attached; at onez end. t one. of.P the wheel studs |l amdnut |5J'.. The: oppositel endi of :the strip; engages: axlesv which: is:l oi course# con neeted. Wit-hi tlrea frame; through,J the. springsl of the; vehicle; ,not shown... By: providing theV1 strip les. the g-roundicimmt @neemt include uneV tear-` mgsf of? the: Wheell which i bearings. might inter'- fer-.eti with the; circuit and whchmight belv sub- Jeeted; to. deleterious electrolytic action by f cur rent dpassingi,thererthrougli-.

Referringznowf-'to Eiga. 12,` thawiring diagram:

- for-sthefmechanismii's shown-.toirinclude pressure responsive; resistance fdevices; |11 6i each' associated Withoner-of therespective four tiresaoftl'ievehicle. It; is to.. bennderstoocb thatmore orf fewerdevicesv could,v beaeprovded.. depending uponf thenumber of tireswdesiredto bechecked-xby thezmechanismt Each of the resistance: wires` |45 is connected with, the;` positiva: terminal; of', the.A battery B through;the:respectivezcollector:ringsf, brushes zfrandiwires l2, ,which latter vWirespare: connected to? tn ezcontacts:A |60 |622; V| G3i respectivelyi ofi arotaryi switch :mechanism: E; which rnechanisml has atsweepingcontact |66; adapted` to4 be rotated?. andi-successively, sweep, theaxed'. contacts; Con'- tactV Iliff.: isiirrzthecircuit of aesolenoid |61; WhichV is.adaptedto rclosefa normallyfopemcontactorr |68.` when. the: soienoidfis;` energized, and? which sole noid circuit: includes; af- Wire 1| andcontact, 10. Contactill. is normally. closed andisfconnected, to,a.resistance L02'. of` a,Wheatst one :bridgewhich;X

the Wh'eatstone bridge shown in Fig.

5, and corresponding parts having corresponding reference numerals with a prime added thereto. The resistance E02 is connected with the positive electrode of the battery B' by wire |12, switch |13, which is similar to switch 18 described hereinbefore and which is opened and closed when the motor ignition switch of the vehicle is opened and closed respectively, and wire |1'l.

By this arrangement it will be seen that by rotating the switch contact Hit the respective resistance coils |45 are successively connected in the Wheatstone bridge circuit and alternately form the fourth arm of the circuit. Rotation of the contact |66 is effected by means to be described hereinafter.

'Ihe bridge of the Wheatstone circuit shown includes an electrical current potential responsive recorder R, which may be any suitable type of commercially7 available instrument having a galvanometer controlled mechanism adapted to record variations in relatively small potentials. A suitable instrument for this purpose is that the Micromax Model S, manufactured by Leeds and Northrup Company, Philadelphia, Pennsylvania, and shown in catalog N-33A, 1949, issued by that company. This instrument includes a scalable housing having a roll or tape of recording paper P mounted therein by mechanism which slowly feeds the paper in alignment with a marking device which is positioned to move laterally of the paper according to the potential balance existing in the bridge. The paper P is suitably lined to indicate normal pressures and a range of tire pressures. llhe marking device is preferably arranged to print a dot on the paper to correspond to tire pressures above or below normal and to print a numeral or other indicia alongside the dots to indicate which tire pressure is represented by the respective dots. In the form shown, the dots are identified by numerals corresponding to the respective lines, as shown.

One terminal of the galvanometer of the recorder R is connected to a terminal |16 of the Wheatstone bridge by wire |11 and the other terminal of the galvanometer is connected to a bridge terminal |18 through wire |19, contactor and wire ll. The power for operating the recorder R is .supplied thereto by a circuit comprising wire |84, which is connected to the battery by way of wire |12, switch |13, wire |14 and ground |85. The recorder includes an electric motor, not shown, which drives the feeding mechanism for the recording strip P and also drives the contact |655 to rota e the same, preferably at approximately l R. P. M. The speed of rotation of contact |56, however, could be of any convenient speed desired.

It will be seen that during normal operation of the mechanism the circuits of resistance coils |45 are individually connected in the bridge circuit once each minute and the recorder R prints a marl: according to the potential in the resistance coil, which potential is a function of the air pressure in the tire involved. In the event no current is passing through the coil due to the contact |-i riding on the insulating bridge Hill, the recorder R will indicate normal tire pressure.

In the event that the air pressure in any tire is above or below normal, the recorder R will record by printing on the strip the exact pressure, and at the same time solenoid i l is energized to close contact |63 which establishes a circuit from the battery through wires |14, |12, |86 to lamp 8S and to ground, which lamp indicates to l0 the vehicle operator the existence of an abnormal air pressure.

Preferably, provision is made whereby the operator may selectively check on the individual tire pressures by referring to an ammeter A. The ammeter A is like the ammeter A and can be selectively connected in the bridge circuit by a switch contact @D which is adapted to close a circuit from bridge terminal |18 through the ammeter and a wire i9| to bridge terminal |18. Contact LSE! is connected to an operating member d3 to which contacts |10 and |80 are also connected. Any one of the resistances |45 may then be set up as the fourth arm of the bridge by a selector switch S which has a manually movable contact connected to the bridge terminal i1@ by a wire |95, which wire includes a suitable resistance |91 corresponding to the resistance of solenoid |61. The switch S' includes four contacts 2013, 20|, 202 and 203 which contacts are connected to the respective wires 12, and by rotating contact |95, the individual resistances |45 can be selectively connected in the Wheatstone bridge circuit whereby the ammeter A' will indicate whether or not the pressures are normal, and if abnormal the exact pressures.

As mentioned previously, the casing of the recorder R is preferably adapted to be sealed or locked so that the record of the tire pressures is available only to an authorized person for inspection. It will be seen that the invention provides relatively inexpensive and reliable means for accurately recording abnormal air pressures in a plurality of vehicle tires and at the same time provides a warning by which the vehicle operator can be immediately apprised of a faulty tire and an indication of the particular tire and the exact so that the seriousness of the situation can be judged at once and without the necessity of stopping the vehicle.

By providing a printed record of the tire pressures, the vehicle operator will be made more aware of the necessity for maintaining proper inflation of the truck tires and the tire supplier has accurate information as to possible abuse of the tires by improper ination thereof.

While in its preferred form, the invention is employed to indicate the air pressure in vehicle tires, it will be appreciated that the invention could be embodied in systems or mechanisms for indicating uid pressures in uid containers other than tires. For example, the invention could be employed to provide a check on pressures within either stationary or moving vats, tanks, boilers and the like, such as those employed for processing various types of materials, or for indicating temperatures by mechanically connecting the movable contact of the resistance devices with suitable thermal responsive elements, such as a bellows lled with thermal responsive iluid.

Having thus described my invention, I claim:

l. In combination with a plurality of pressurized containers; a source of electric current, an electric circuit connected to said source; a separate means operatively associated with each container and adapted to be electrically connected with said circuit and responsive to the pressure in the respective container and each provided with cooperating elements that regulate the current flow value through the respective separate means and said circuit in correlation to the pressure in the respective container when such pressure is above or below a predetermined pressure range but interrupt current ilow therethrough when the pressure in the respective coneinsam tainer vis Within lsa'id predetermined '.range; w. signal circuit connected to said electric circuit, a :single electrically responsive 'signal device AKincluded in said signal circuit, "meansior .fautomatically completing said signal 'circuitand-energizing `said single v'device in response Ito fa current fow through any of fsaid l'separate means and -said electric 'circuit "thus "warning Tdi 'the existence in atleast vone loi the A'containersfoi fa pressure which is above-or belcwis'aid predetermined pressure range; asingle'indicating .device connected to said `electriccircuit and adapted 'to show =the current 'value `iiowing ythrough Zsaid electric circuit and any of Y'said separate means andcalibrated in terms of pressureandselecting means included'in'said electric circuit :for .'s'el'ectively connecting said single 'indicating device with 'the individual .separate means whereby when said signal' device is energized "said'selecting means enables determination .oi the particular container whereinthe i"pressurelisabove'cr below the 'predetermined fpressure range.

12. The'combinationdeiined in claim l and including 'switch 'means for connecting vxsaid 'separatemeans "to'said electri'cfcircuit, l'an indicating circuit connectedl to "-sa'id electric 'circuit and fcontaining said 'single indicating device, switchmeans in said Vindicating `.circuit to "openan'd close .the same, and ya selector switch "means connected 'to said indicating circuit and rall -toi said separate means 'and enabling :the flatter Ato be 'selectively connected into "the E'indicating circuit, said'rst named -switch means Ebeing frendered ineffective when said indicating'circuit is closed by the'fswlt'ch meanstherein.

'3. The combination defined in "claim 2 and including an electricalrecording mechanism :connected to =said electric circuit and automatically recording the pressures in fsaid containers xvwhen the same are above for below .said predetermined pressure range provided ".said ii'rst vzi'iamed switch means -is/ effective itc connectisaidseparatefmeans with said 'felectricfcircui f4. 4The `comicmation "deiined iin claim ".3 land wherein said first named switch means iis 'f automatically 'operated by.saidvrecordingrnechanism and successively and Iautomatically lconnects fsaid separate' means -Awith fsa'rdielectric circuit.

'5. IIn 'combination with ia "plurality olf'pr'essurized containers; 'separate ldei/"ices "corresponding in'nurnber to "said containers, l'with 'onelsuclideih vice 'operatively associated 1with each fcontainen said devices `being responsiveto ithe pressures 'in the respective containers; fan 'electric fc'ircuit, fa source of 'electrical fenergy comiected' to said fuircuit, `parallel circuits corresponding in number to l'said separate devices fand reach 'including #one oi 'said devices, ^a 'firstv switchimeans 'ffcr "connecting said 'parallel fcircuitsfto .said l'electric fcircu'it, each device being ipr'ovided with cooperating elements that feffect fcurrent iiow through `the 1respective separate device andthe parallel circuit containing the tsame and .said electric circuit whenrsaid iirst :switch lirrizeansfis-closed ci iaualue correlated tothe pressure iinitlffe respedzivefccntainer when such pressure 'is -Fa'bove lfor ibelow .fa predetermined'pressure range ibut finterrupt current flow therethrough when ctire pressureinzthe l means is effective to connect I2 respective-contenteriistwithinzsaidpredetermined range; a signal rcircut i connected 'to .said electric circuit and parallel thereto `andcontaining a single signalidevice, said electric circuit kand .said signal circuit havingcoperatingi meansiior'automaticallyiclosingsaidsignal circuit'and energizing saidsingle .signal "device inresponser to 1a current flow through anytfof said 'separate devices, .the parallel circuits containing .the ."same, Aand zsaid electric r`circuit but vautomatically opening said signal circuit when' there isrn'o current'flowitherethrough; and indicating circuit connectedto said electric 7.circuit fand containing ai single vindicating devicefadaptedto showthe current Avalue fflowing through said indicating circuit'andcalibratedin terms -voi pressure, vva :selector fswitch electrically connected'toeach of saidparallelfcircuits an'dfsaid separate'devices, and means electrically connectingsaidzindicating circuit and-"said selector 'switch and in'cluding fa :switch adaptedlto fb'e open when said 'iirst .named switch is eiective yand closed when said'i-lrstnamed switchtis ineiiective.

'6.'The combination defined in rclaim 5 and Whereinisaid rst'switch'means and -said vswitch in vthe jmeans lior electrically 'connecting said in dicat'ing circuit and said selector switch are 'articulated such that V'closing "of v'said 'first switch means opens "said switch'and vice versa.

17. "The combination dei'rled in claim '5 :and wherein' thefcooperating means for automatically closingtsaid .signal circuit `includes :a solenoid in said electric `circuit "and a znormally Yopen ccntaeter 'in said signal y"circuit `that 'is closed 4when said solenoid is energize'dby current flow'throug'h said electric icircuit.

`8.'The combination defined in .claim 5 and wherein an V'electrical recording mechanism lis connected to said electric #circuit and automatn cally records Y:the pressures "in 'said 'containers when the same "are 'above or `below said predetermined 'pressure range V'provided said "iirst `switch said parallel circuits lwith said electric circuit.

y:9. The combination 'delined 'in 'claim 3 and wherein said first lswi'tchl means is automatically operated "by 'said '.recordingmeclianism and in lude'sispaced'contacts 'connected to said parallel circuits 'and fa sweeping con'tact )arm successively engaging fsa'id spaced contacts.

TDVID M. 'LENTE lReferences 'Cited .in the file of .this .patent UNITED STVI'ES PATENTS Number "Name Date 12954,l5`3 Taylor Aprfl, 193e4 2248;047 Aduyet al July 8,1941 '2270,1'48 Stowe J an. 13, '15942 2,353,428 Akin July ll, '1944 2,'4'23,247() Pelletterie July 1, 1947 A231:2'3 ,659 iMi'dle'ffon 'etal July 8, 1947 j2;:43'91l92 vLindstrom Api'. l(i, 1948 2,443,252 r`Kelly July l5, 1948 '2;55'0j04'1 "Cozzolino etfal Apr. '24, 1951 2,15%,224 `Uttelb3lkft al. vApr. 15,'1-952 FOREIGN .PATENTS Number -Country `Date 5532821 Great Britain -June '7, 1943 

